Peracid compositions have been reported to be effective antimicrobial agents. Methods to clean, disinfect, and/or sanitize hard surfaces, meat products, living plant tissues, and medical devices against undesirable microbial growth have been described (U.S. Pat. No. 6,545,047; U.S. Pat. No. 6,183,807; U.S. Pat. No. 6,518,307; U.S. patent application publication 20030026846; and U.S. Pat. No. 5,683,724). Peracids have also been reported to be useful in preparing bleaching compositions for laundry detergent applications (U.S. Pat. No. 3,974,082; U.S. Pat. No. 5,296,161; and U.S. Pat. No. 5,364,554).
Peracids can be prepared by the chemical reaction of a carboxylic acid and hydrogen peroxide (see Organic Peroxides, Daniel Swern, ed., Vol. 1, pp 313-516; Wiley Interscience, New York, 1971). The reaction is usually catalyzed by a strong inorganic acid, such as concentrated sulfuric acid. The reaction of hydrogen peroxide with a carboxylic acid is an equilibrium reaction, and the production of peracid is favored by the use of an excess concentration of peroxide and/or carboxylic acid, or by the removal of water. There are several disadvantages to the chemical reaction for peracid production: 1) the high concentration of carboxylic acid used to favor production of peracid can result in an undesirable odor when using the peracid-containing solution, 2) the peracid is oftentimes unstable in solution over time, and the concentration of peracid in the solution decreases during storage prior to use, and 3) the formulation is often strongly acidic due to the use of a concentrated sulfuric acid as catalyst.
One way to overcome the disadvantages of the chemical production of peracids is to employ an enzyme catalyst in place of a strong acid catalyst. The use of an enzyme catalyst allows for the rapid production of peracid at the time of use and/or application, avoiding problems associated with storage of peracid solutions and variations in peracid concentrations over time. The high concentrations of carboxylic acids typically used to produce peracid via the direct chemical reaction with hydrogen peroxide are not required for enzymatic production of peracid, where the enzyme-catalyzed reaction can use a carboxylic acid ester as substrate at a much lower concentration than is typically used in the chemical reaction. The enzyme reaction can be performed across a broad range of pH, dependent on enzyme activity and stability at a given pH, and on the substrate specificity for perhydrolysis at a given pH.
Esterases, lipases, and some proteases have the ability to catalyze the hydrolysis of alkyl esters to produce the corresponding carboxylic acids (Formula 1):

Some esterases, lipases, and proteases also exhibit perhydrolysis activity, catalyzing the synthesis of peracids from alkyl esters (Formula 2):

O. Kirk et al. (Biocatalysis, 11:65-77 (1994)) investigated the ability of hydrolases (lipases, esterases, and proteases) to catalyze perhydrolysis of acyl substrates with hydrogen peroxide to form peroxycarboxylic acids, and reported that perhydrolysis proceeds with a very low efficiency in aqueous systems. Furthermore, they found that lipases and esterases degraded percarboxylic acid to the corresponding carboxylic acid and hydrogen peroxide. They also found that proteases neither degraded nor catalyzed perhydrolysis of carboxylic acid esters in water. The authors concluded that esterases, lipases and proteases are, in general, not suitable for catalyzing perhydrolysis of simple esters, such as methyl octanoate and trioctanoin, in an aqueous environment.
U.S. Pat. No. 3,974,082 describes the production of bleaching compositions for laundry detergent applications by contacting the material to be bleached with an aqueous solution containing an oxygen-releasing inorganic peroxygen compound, an acyl alkyl ester, and an esterase or lipase capable of hydrolyzing the ester.
U.S. Pat. No. 5,364,554 describes an activated oxidant system for in situ generation of peracid in aqueous solution using a protease enzyme, a source of hydrogen peroxide, and an ester substrate that is preferably chemically non-perhydrolyzable. A method of bleaching and a method of forming peracid are also disclosed.
U.S. Pat. No. 5,296,161 describes production of peracid in an aqueous solution comprising one or more specific esterases and lipases, a source of hydrogen peroxide, and a functionalized ester substrate suitable for use in a bleaching composition. However, the concentration of peracid produced was generally insufficient for use in many commercial disinfectant applications.
Most known methods for preparing peracids from the corresponding carboxylic acid esters using enzyme catalysts do not produce and accumulate a peracid at a sufficiently high concentration to be efficacious for disinfection in a variety of applications. Several protease and lipase combinations have recently been reported to generate peracids (e.g., peracetic acid) in situ at concentrations suitable for use as a disinfectant and/or commercial bleaching agent (see co-owned U.S. patent application Ser. Nos. 11/413,246 and 11/588,523; herein incorporated by reference). However, there remains a need to identify additional perhydrolase catalysts capable of producing peracids in situ.
U.S. Pat. No. 4,444,886 describes a strain of Bacillus subtilis (ATCC 31954™) having ester hydrolase activity (described as a “diacetinase”) that has high specificity for hydrolyzing glycerol esters having acyl groups having 2 to 8 carbon atoms. U.S. Pat. No. 4,444,886 does not describe, discuss or predict that the ester hydrolase activity of this strain has perhydrolase activity towards carboxylic acid esters, including glycerol esters.
The problem to be solved is to provide a process to enzymatically produce peracids in situ at concentrations suitable for use in a variety of disinfectant applications and/or bleaching applications. Preferably, the substrates used to produce the peracid compositions should be relatively non-toxic and inexpensive, such as carboxylic acid esters, especially mono-, di-, and triacylglycerols, wherein the acyl group has 1-8 carbon atoms, as well as acetylated sugars and C1 to C6 polyol esters.